Device for supporting a wafer

Abstract

A device for supporting a wafer comprises a base plate for arranging the wafer thereabove and a plurality of supports circumferentially arranged on the base plate to support the peripheral of the wafer. In order to expose portions of the wafer covered by the supports, either an annular member to engage with the supports for moving them radially outward, or a roller driven by a motor to rotate the wafer relative to the supports is provided.

We claim: 
     
       1. A device for supporting a wafer, comprising: a base plate;   a group of first supports circumferentially arranged at regular intervals on said plate to support a periphery of the wafer above said plate, and a group of second supports circumferentially arranged on said plate, in spaced relation to each of the first supports, to support the periphery of the wafer above said plate, each of the first and second supports being movable between a supporting position for supporting the wafer and a releasing position, radially outward of said supporting position, in which the support is released from the wafer;   releasing means urging each of said first and second supports radially outwardly toward said releasing position; and   means for alternatively (1) moving each of said first supports into said supporting position while simultaneously allowing said releasing means to urge each of said second supports into said releasing position or   (2) moving each of said second supports into said supporting position while simultaneously allowing said releasing means to urge each of said first supports into said releasing position, said alternatively moving means including an annular member rotatably mounted on said base plate, said annular member having a plurality of internal projections circumferentially arranged along an inside surface of said annular member in correspondence with said first and second supports.     
     
     
       2. A device according to claim 1, wherein each of said first and second supports can occupy said supporting position by an engagement thereof with the corresponding internal projection. 
     
     
       3. A device according to claim 2, wherein each of said internal projections has a contour inclined to the inside surface of said annular member. 
     
     
       4. A device according to claim 3, wherein a direction of inclination of the contour of one internal projection is opposite to a direction of inclination of the contour of the neighboring internal projection. 
     
     
       5. A device according to claim 1, wherein each of said supports is provided with a groove by which the wafer is rotatably supported.